Everything set up and flying great in 3GX mode. APS install as planned, including calibration and vibe test (this problem is not the documented tail wag each way if trying to enter APS without doing vibe test)

Heli will sit there just fine for about 5 to 10 seconds in APS mode, then a sudden tail twitch of maybe 20 degrees to one side. It almost seems heli is getting a stray rudder input.

Rudder subtrim and trim both at zero. Playing with trim, we can get tail to tick to the other side, but cant seem to get it stable. There is a seemingly random tail kick going on.

Ive redone the APS unit mounting tape. Now using Zeal tape. Same results. Even tried playing with APS mode gyro gain but that does not seem to make a difference either. All is good and this problem does not happen in 3GX mode, so it must be an APS unit issue of some type.

600ESP with DFC and TT (all gears good) and has passed three separate vibe tests (never failed one). All good but this tail problem in APS (and GPS modes).

Hey thanks HedgeHeli, but seems the problem follows the APS gyro's engagement. No issues at all when flying under 3GX. I think im going to take APS out and install it on my 700e 3GX instead. If still same problem there, I think I may have to get in touch with Align because it that point, we must have a bad APS unit?

I'm having the same issue you described: take off in 3GX mode normally, then switch to APS mode and the heli stabilizes. Then, after a few seconds, tail start waging and heli starts to drift.

I was thinking... I'm activating 3GX/APS/GPS using the gyro gain on my Spectrum DX8, through Rudder D/R 3-position switch. It is set like this:

Pos 0: +50% = 3GX mode
Pos 1: 0% = APS mode
Pos 2: -20% = GPS mode

Doesn't that means I'm disabling/lowering gyro gain when changing to APS mode? Or APS just ignore gyro gain and uses it only for knowing the current mode?

Further more, I'm not using a completely straight horizontal line as the throttle curve for the APS/GPS modes, since I'm considering the heli will need more throttle when more pitch is needed, so I'm using a curve like this:

Hello Alex. The parasite is the main problem of the aps, very very sensitive. You should check if your wire from the aps box is located outside of the body left side. That it be as far as possible on the elevator servo. Then downloaded the aps v.1.2. Then you have to put the min the gain of the axis of tail on the aps module. Don't forget to reprogram the modes of the aps

Yesterday, during the flight test, I found I had the Anti Torque Compensation wrongly configured on the 3GX. It was set up for using 3GX upside down. I changed it and now APS seems to be stabilizing very well. Further tests will be done, but I'm very happy with the results up to now.